The invention relates to components made of steel for establishing contact with rolling contact members, more particularly outer joint parts (2) and inner joint parts (3) of constant velocity joints, as well as sleeves and journals of ball-guided longitudinal plunging pieces, and to a process of heat-treating such components.
In constant velocity joints with an outer joint part and an inner joint part and with torque transmitting rolling contact members which are held in running grooves in the outer part and inner part and roll therein, there occur high pressures between the rolling contact members and the running grooves in the inner part and outer part. Such loads which are present in the form of Hertzian pressure can lead to the formation of pitting which, in the final analysis, causes the constant velocity joints to fail. Similar conditions prevail in the case of ball-guided longitudinal plunging pieces provided for torque transmitting purposes wherein sleeves and journals each comprise longitudinal grooves in which balls are held and in which the balls roll.
In U.S. Pat. No. 4,741,785, there is known a process for partially surface-hardening running grooves in the outer joint part and inner joint part of a constant velocity ball joint wherein the contact faces of the running grooves and of the cage, which contact faces guide the balls, are hardened by means of a formed inductor. The depth of hardness of the running grooves amounts to 0.5 mm. The guiding faces of the inner joint part and of the outer joint part, which guiding faces are positioned between the running grooves and serve to guide the cage, are hardened by a second hardening process which produces smaller depths of hardness. For this purpose there are provided laser or electron beam hardening processes or, alternatively, thermo-chemical surface hardening process such as nitriding.